Ignition of boron-based green hypergolic fuels with hydrogen peroxide

Abstract

Exploring novel green hypergolic fuels ignited with hydrogen peroxide (H2O2) offers a number of opportunities in space propulsion with regard to replacing conventional toxic propellant combinations. The green hypergolic fuels, BH bond-rich zwitterions and ionic liquids (ILs) were synthesized; their hypergolic reactivity was investigated with 95% H2O2. Remarkably, ammonia borane (AB) and 1-ethyl-3-methyl imidazolium borohydride ([EMIM][BH4]) exhibited the lowest ignition delay times of 8.1 and 18.5 ms, respectively. For a comprehensive application, the reactivity of liquid and hybrid fuel blends were studied. A liquid fuel blend, [EMIM][BH4] and methyl imidazolium borane (MIMB) (1:1, w/w) exhibited the ignition delay time of about 35 ms. Further, a solid hybrid fuel blend consisting of 40% AB-paraffin revealed a hypergolic ignition delay time of 9.2 ms. Additionally, the gas phase heat of formation and specific impulse were calculated using G09 and NASA-CEC-71 programs, respectively. The specific impulse of AB was 273 s, which is higher than the stated hypergolic zwitterions. Hence, the BH bond-rich zwitterions and ILs are promising choices for new generation green hypergolic liquid and hybrid rocket propulsion.